CN109575109B

CN109575109B - Method for preparing degarelix by fragment condensation

Info

Publication number: CN109575109B
Application number: CN201811617676.XA
Authority: CN
Inventors: 彭雅丽; 王锐; 贺真; 方泉; 许兆青
Original assignee: Lanzhou University
Current assignee: Lanzhou University
Priority date: 2018-12-27
Filing date: 2018-12-27
Publication date: 2022-03-25
Anticipated expiration: 2038-12-27
Also published as: CN109575109A

Abstract

The invention discloses a method for preparing degarelix by fragment condensation, which comprises respectively synthesizing 3 peptide fragment sequences protected by side chains, gradually coupling each peptide fragment to obtain fully-protected degarelix, then cracking to remove protecting groups to obtain crude degarelix peptide, purifying and changing salt to obtain degarelix; wherein, the sequence of the 3 peptide fragments is as follows: the first peptide fragment sequence is the 1 st to 4 th amino acids in the degarelix sequence, the second peptide fragment sequence is the 5 th to 8 th amino acids in the degarelix sequence, and the third peptide fragment sequence is the 9 th to 10 th amino acids in the degarelix sequence. The method reduces impurities, improves the yield, greatly reduces the synthesis cost and is beneficial to large-scale and industrialized production.

Description

Method for preparing degarelix by fragment condensation

Technical Field

The invention relates to the field of pharmacy, in particular to a method for preparing degarelix by fragment condensation.

Background

Degarelix, english name: degarelix, a decapeptide containing seven unnatural amino acids in the sequence: Ac-D-2Nal-D-Phe (4Cl) -D-3Pal-Ser-4Aph (hor) -D-4Aph (Cbm) -Leu-ILys-Pro-D-AIa-NH₂. Degarelix is a third generation gonadotropin releasing hormone (GnRH) receptor antagonist, useful for the treatment of prostate cancer, with rapid onset of action, suppression of gonadotropins, testosterone and prostate specific antigens.

The synthesis of degarelix is described in US5925730, where the preferred alpha-amino protecting group is tert-butyloxycarbonyl (Boc), which is removed under acidic conditions by standard treatment with trifluoroacetic acid (TFA). The defects are that TFA has high toxicity, pollutes the environment and has high post-treatment cost; moreover, high proportions of TFA cause the peptide to be detached from the resin, and repeated use of TFA adds this effect, increasing losses and reducing yields. Meanwhile, the peptide resin needs HF cracking, HF is extremely toxic and has strong corrosivity, great harm is caused to people and the environment, and great potential safety hazard is caused to large-scale industrial production. Therefore, fluorenylmethyloxycarbonyl (Fmoc) is more used for alpha-amino protection in industrial production.

The 5-amino acid Aph (hor) in degarelix. Under basic conditions, compounds containing a dihydrouracil moiety undergo rearrangement to a compound containing a hydantoin moiety. Therefore, during the synthesis of degarelix, the intermediate Fmoc-4Aph (hor) -D-4Aph (Cbm) -Leu-ILys-Pro-D-Ala-NH-resin is partially rearranged during deprotection under alkaline conditions to become Fmoc-X-D-4Aph (Cbm) -Leu-ILys-Pro-D-Ala-NH-resin, and X is 4- ([2- (5-hydantoinyl) ] -acetylamino) -phenylalanine. Therefore, basic conditions should be avoided as much as possible in the manufacturing process of pharmaceutical grade degarelix using the protecting group Fmoc. In patent CN102428097, Fmoc strategy solid phase method is adopted to sequentially synthesize degarelix by connecting, piperidine is used for removing Fmoc, but the repeated deprotection process is contacted with alkaline conditions, so that the appearance of impurities (0.1-0.3%) can be reduced, and the problem cannot be solved.

In patent CN102329373, degarelix is synthesized by sequentially connecting through Fmoc strategy solid phase method, 5-site amino acid is protected by Trt or Alloc, and after the synthesis of linear chain peptide is finished, side chain protection is removed and Hor is coupled. However, the removal of the protecting group Trt of the amino acid residue 4Aph (Trt) by using 5-10% TFA/DCM results in the removal of the protecting group Boc of the 3 rd amino acid residue Lys (ipr, Boc), so that the naked amino group reacts with L-4, 5-dihydroorotic acid to generate new impurities; pd (Ph) is used for removing the protecting group Alloc of amino acid residue 4Aph (Alloc)₃P)₄Phenyl silane/DCM, Pd (Ph)₃P)₄The price of (2) is expensive, which increases the cost of mass production. Meanwhile, the yield of Trt or Alloc protected amino acid including Cbm protected 6-site amino acid is very low in liquid phase synthesis, and the difficulty and cost of purification are greatly increased by more impurities in liquid phase synthesis. The substitution value of the solid phase carrier is limited, so that the total yield is low; amount of amino acid addedHigh, the synthesis cost is high; more impurities and high purification cost.

CN102952174, CN103992378, CN103992392, CN104177478, CN 105085635, CN105524143 and CN107344960 adopt Fmoc strategy solid phase method to connect and synthesize degarelix in turn, and the substitution value of solid phase carrier is limited to cause lower total yield; the amino acid dosage is high, and the synthesis cost is high; more impurities and high purification cost.

The patent CN103351428 and the patent CN107022002 are synthesized by a solid phase fragment condensation method, each fragment input by the solid phase fragment condensation is 2 times of the excessive amount, peptide fragments are seriously wasted, and the synthesis cost is very high; meanwhile, the substitution value of the resin of the solid-phase fragment condensation is limited, the material flux is reduced, the solvent is wasted, and a large amount of waste liquid is generated.

Patent CN103180335 is synthesized by 3+4+3, patent CN106589071 is synthesized by 6+4 liquid phase fragment condensation, wherein each fragment is also synthesized in liquid phase, and it can be seen that each step of coupling reaction involves tedious N-terminal and C-terminal protection and deprotection processes, and proper pH condition coordination, which generates large workload and waste liquid discharge, takes a long time, and the efficiency of liquid phase synthesis of peptide fragments is far lower than that of solid phase synthesis of peptide fragments, and the separation is also difficult.

It can be seen that most of the research on the synthesis method of degarelix focuses on reducing impurities and improving purity, but in practice, the prior art processes can obtain pure peptides with pharmaceutical grade requirements through one or more preparations. The use of more expensive amino acid protecting groups or condensing agents simply to increase purity is not meaningful to the practical demands of scale-up and industrial production. As described above, since degarelix contains seven unnatural amino acids in the sequence thereof at a unit price several times or several tens times higher than that of natural amino acids, the synthesis cost of degarelix is very high, and it is considered that a new synthesis method for reducing the synthesis cost and reducing the generation of waste liquid by reducing the synthesis cost even at the expense of a part of the yield while ensuring the product yield and product purity is very necessary and important for large-scale and industrial production.

Disclosure of Invention

The invention aims to solve the technical problems that the existing method is low in synthesis yield, high in product impurity, high in production cost and incapable of efficiently obtaining high-purity degarelix at low cost, and provides a method for preparing degarelix by fragment condensation.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows:

the method for preparing degarelix by fragment condensation comprises the steps of synthesizing a first peptide fragment sequence protected by a side chain and a second peptide fragment sequence protected by the side chain in a solid phase manner, synthesizing a third peptide fragment sequence protected by the side chain in a liquid phase manner, gradually coupling each peptide fragment to obtain fully-protected degarelix, then cracking and removing a protecting group to obtain crude degarelix, and purifying and changing salt to obtain degarelix;

wherein the content of the first and second substances,

the first peptide fragment sequence is the 1 st-4 th amino acid in the degarelix sequence,

the second peptide fragment sequence is the 5 th-8 th amino acid in the degarelix sequence,

the third peptide fragment sequence is the 9 th-10 th amino acid in the degarelix sequence.

The method for preparing degarelix by the fragment condensation preferably comprises the following steps:

(1) respectively synthesizing a first peptide fragment sequence with protected side chain and a second peptide fragment sequence with protected side chain by a solid phase, and cracking from resin;

(2) liquid phase synthesis of a side chain protected third peptide fragment sequence;

(3) coupling the third peptide fragment sequence without the amino protecting group and the second peptide fragment sequence with the side chain protection to obtain a fourth peptide fragment sequence with the side chain protection, and removing the amino protecting group;

(4) coupling the side chain protected fourth peptide fragment sequence without the amino protecting group and the side chain protected first peptide fragment sequence to obtain fully protected degarelix;

(5) cracking the fully protected degarelix to remove a protecting group to obtain a degarelix crude peptide;

(6) the crude degarelix peptide is purified and the salt is changed to obtain the degarelix.

In step (1), the sequence of the first peptide fragment having side chain protection is Fmoc-D-3Pal-Ser (. psi.) (Fmoc-D-3 Pal-Ser)^Me，Me) Pro-OH, Fmoc-D-Phe (4-C1) -OH and Ac-D-Nal-OH are coupled on a solid phase carrier in sequence to obtain; wherein, the solid phase carrier is acid-sensitive resin, preferably 2-chloro-trityl chloride resin.

In the solid phase synthesis of the sequence of the first peptide fragment with side chain protection, an amino deprotection reagent is a DMF solution with 20 percent of piperidine by volume or a DMF solution with 1 percent of DBU by volume; a20% by volume solution of piperidine in DMF is preferred.

The coupling agent is a combination of DIC and HOBt according to the molar ratio of 1: 1, or a combination of HBTU and HOBt and DIEA according to the molar ratio of 1:2, or a combination of PyBOP and HOBt and DIEA according to the molar ratio of 1: 2; preferably HBTU, HOBt and DIEA are combined according to the molar ratio of 1: 2; the molar ratio of amino acid to be coupled to HOBt was 1: 1.

The cracking agent is a DCM solution containing 0.5-1% of TFA by volume percentage, or a DCM solution containing 20% of TFE by volume percentage, or a mixture of TFE, AcOH and DCM in a volume ratio of 1:2:7, and preferably a DCM solution containing 0.5-1% of TFA by volume percentage.

In the step (1), the second peptide fragment sequence with side chain protection consists of Fmoc-ILys (Boc) -OH, Fmoc-Leu-OH and Fmoc-D-Phe (4-NO)₂) Coupling OH on a solid phase carrier in sequence, then reducing peptide Resin, and connecting side chain for protection to obtain peptide Resin Fmoc-D-4Aph (Cbm-tBu) -Leu-ILys (Boc) -Resin; then the peptide resin removes Fmoc protection and amino-terminal coupling Fmoc-Phe (4-NO)₂) OH, then reducing the peptide Resin, and carrying out side chain protection to obtain Fmoc-4Aph (hor) -D-4Aph (Cbm-tBu) -Leu-ILys (Boc) -Resin; wherein, the solid phase carrier is acid-sensitive resin, preferably 2-chloro-trityl chloride resin.

In the solid phase synthesis of the sequence of the second peptide fragment with side chain protection, an amino deprotection reagent is a DMF solution of piperidine with the volume percentage of 20% or a DMF solution of DBU with the volume percentage of 1%; a20% by volume solution of piperidine in DMF is preferred.

In the step (2), the sequence of the side chain-protected third peptide fragment is Fmoc-Pro-D-Ala-NH₂From Fmoc-Pro-OH and D-Ala-NH₂Coupling in liquid phase; the coupling agent used is a combination of HBTU and HOBt and DIEA in a molar ratio of 1:2, or a combination of HBTU and HOAt and DIEA in a molar ratio of 1:2, or a combination of DIC and HOBt in a molar ratio of 1: 1, or a combination of EDC and HOBt in a molar ratio of 1: 1, or a combination of PyBOP and HOBt and DIEA in a molar ratio of 1: 2. Preferably HBTU and HOBt and DIEA are combined in a molar ratio of 1: 2. The molar ratio of the carboxyl terminal to be coupled to the amino terminal is 0.95-1.05: 1. The molar ratio of the carboxy terminus to be coupled to HOBt was 1: 1. The solvent for the coupling reaction is any one or a combination of DMF, DCM, NMP, THF, TFE and DMSO, and DMF is preferred.

In the step (3), the amino deprotection reagent is a DMF solution of piperidine with the volume percentage of 16% or a DMF solution of DBU with the volume percentage of 1%. A DMF solution with a 16% by volume content of piperidine is preferred.

In the steps (3) and (4), the coupling agent used is a combination of HBTU, HOBt and DIEA according to the molar ratio of 1:2, or a combination of HBTU, HOAt and DIEA according to the molar ratio of 1:2, or a combination of DIC and HOBt according to the molar ratio of 1: 1, or a combination of EDC and HOBt according to the molar ratio of 1: 1, or a combination of PyBOP and HOBt and DIEA according to the molar ratio of 1: 2. Preferably HBTU and HOBt and DIEA are combined in a molar ratio of 1: 2. The molar ratio of the carboxyl terminal to be coupled to the amino terminal is 0.95-1.05: 1. The molar ratio of the carboxy terminus to be coupled to HOBt was 1: 1. The solvent for the coupling reaction is any one or a combination of DMF, DCM, NMP, THF, TFE and DMSO, and DMF is preferred.

In step (5), the lysis solution of the full protection degarelix is TFA and H₂Mixed solution of O in the volume ratio of 95:5, or TFA, EDT, TIS, PhOH and H₂Mixed solution of O in the volume ratio of 80:5, or TFA and EDT and TIS and H₂O in a mixed solution of TFA and EDT and TIS and H in a volume ratio of 92.5:2.5₂O is mixed solution according to the volume ratio of 92.5: 2.5.

In the step (6), the purification is reversed-phase high performance liquid chromatography purification salt exchange, namely a chromatographic column is a C18 column; the mobile phase is 0.25 percent by volume of acetic acid water solution and acetonitrile.

Has the advantages that:

compared with the prior art, the invention has the following advantages:

1. the invention uses acid-sensitive resin with high load capacity as the initial raw material, firstly adopts the standard solid phase peptide synthesis technology to synthesize high-purity peptide fragments, and then adopts the liquid phase coupling technology to condense the peptide fragments, thereby obtaining the target peptide with high purity (more than 99.89%) and high yield (more than or equal to 70.3%).

2. Compared with the process of synthesizing the degarelix by solid phase condensation one by one, each segment of the method can use a solid phase carrier with high load capacity, the resin substitution value is high, the resin substitution value limitation caused by excessive number of the amino acids condensed one by one is avoided, the material flux is increased, and the waste liquid discharge is reduced. After fragmentation, the synthesis of each peptide fragment can be carried out simultaneously, greatly shortening the synthesis time. Fragment coupling, the impurities of which are mainly uncoupled fragments, rather than defective peptides lacking one or several amino acids, is much easier in the final purification by high performance liquid chromatography, thus reducing the number of preparations and the cost of the preparation.

3. Compared with the process for synthesizing degarelix by solid-phase fragment condensation, the invention utilizes liquid-phase fragment condensation, the molar ratio of the fragments is 0.95-1.05 times, and the molar ratio is far less than 2 times of the molar ratio of the fragments synthesized by solid-phase fragment condensation, so that the material cost is saved; and unreacted fragments can be extracted and removed through a proper reaction system, and the post-treatment is simple and quick. And the liquid phase segment condensation does not have the problem of resin substitution value limitation existing in solid phase segment condensation, the material flux is increased, and the generation of waste liquid is reduced.

4. In experiments, the degarelix 4-amino acid Ser or 5-Aph (hor) as the carboxyl end of fragment condensation generates a racemic byproduct, which is caused by the nature of the amino acid, so that the Fmoc-D-3Pal-Ser (psi) is adopted in an attempt^Me，Me) Pro-OH to eliminate racemic by-products. The experiment result shows that the reasonable segmentation scheme and the protection strategy of the invention well solve the problem, avoid racemization under the condition of not reducing yield, reduce by-products and improve the purity of crude peptide.

5. The 5-amino acid aph (hor) of degarelix rearranges under basic conditions a compound containing a dihydrouracil moiety to a compound containing a hydantoin moiety, which is the main impurity of degarelix. The invention reduces the possibility of the impurity to the minimum through reasonable fragment segmentation, and improves the purity of the peptide; and after the fragment condensation is adopted, the material flux is further improved, the generation of waste liquid is reduced, and the synthesis cost is reduced, which is an unexpected result.

6. The cost of the invention is only 1/3-1/2 of the existing process, and the cost is greatly reduced. The prior art adopts amino resin, and the invention adopts super acid-sensitive resin, the price of which is 1/4 of the amino resin. In the synthesis of the first peptide fragment, Fmoc-D-3Pal-Ser (psi) was attached to a solid support^Me，Me) Pro-OH, wherein Fmoc-D-3Pal-OH is expensive, only 1 time of equivalent is needed to be added as the first amino acid for resin coupling, but not 2 times or even 3 times of equivalent which is usually needed, and the cost is reduced by 1/2-2/3. In the synthesis of the second peptide fragment, Fmoc-ILys (Boc) -OH connected with a solid phase carrier is expensive, the first amino acid used for resin coupling only needs to be added by 1 time of equivalent, but not by 2 times or even 3 times of equivalent, and the cost is reduced by 1/2-2/3. Fmoc-4Aph (H) in position 5 of degarelix sequenceor) -OH and 6-Fmoc-D-4 Aph (Cbm-tBu) -OH are very expensive and can account for half of the cost of amino acid, and Fmoc-Phe (4-NO) is adopted in the invention₂) -OH and Fmoc-D-Phe (4-NO)₂) OH as starting material to accomplish reduction and side chain modification of immobilization, and Fmoc-Phe (4-NO)₂) -OH and Fmoc-D-Phe (4-NO)₂) The price of-OH is only 1/10 of the price of Fmoc-4Aph (hor) -OH and Fmoc-D-4Aph (Cbm-tBu) -OH, which greatly reduces the cost; compared with liquid phase synthesis of amino acid, the method has the advantages of improving yield and purity, saving time and reducing waste liquid of post-treatment; the purity of the peptide fragments obtained was high, which was an unexpected result.

The method has the characteristics of high flux, less waste liquid, less impurities, easy purification and high yield, avoids directly purchasing or synthesizing expensive unnatural amino acid in a liquid phase, and effectively reduces the production cost. The invention originally aims at reducing the synthesis cost, and even expectedly can sacrifice part of the synthesis yield, but surprisingly obtains the degarelix production process with high yield and high purity on the basis of effectively reducing the cost, and is very suitable for large-scale and industrialized production.

The amino acid sequences of the respective peptide fragments of the target peptide (degarelix) and the intermediate according to the invention are shown in table 1.

The meanings of the abbreviations used in the present invention are shown in Table 2.

TABLE 1 corresponding encoded amino acid sequences of degarelix

TABLE 2 abbreviations for materials used in the present invention

Drawings

FIG. 1 shows the spectrum of degarelix prepared according to the invention.

FIG. 2 is a degarelix chromatogram prepared in accordance with the present invention.

Detailed Description

The invention will be better understood from the following examples. However, those skilled in the art will readily appreciate that the description of the embodiments is only for illustrating the present invention and should not be taken as limiting the invention as detailed in the claims.

Example 1:

1. resin preparation

1.1 preparation of Fmoc-D-3Pal-Ser (psi)^Me，Me) Pro-2-chloro-trityl resin: 2-chloro-trityl chloride resin (10g, substitution 1.03mmol/g resin, leq) was added to the polypeptide synthesizer and the resin was washed with 100mL DCM. The solvent was drained and Fmoc-D-3Pal-Ser (psi) was added^Me，Me) Pro-OH (1.1eq) and DIEA (2.5eq) in 50mL DCM. The mixture was mechanically stirred for 1 hour under argon. The active fraction on the resin was blocked for 30 minutes by adding 20mL of chromatographic methanol (2mL/g resin). The solvent was drained, washed with 3X 80mL of DMF, 3X 80mL of DCM, 3X 80mL of MeOH, and dried in vacuo to constant weight to give 14.7g of Fmoc-D-3Pal-Ser (psi)^Me，Me) Pro-2-chloro-trityl resin. The Fmoc amount in the piperidine deprotection solution was measured by UV spectrophotometry, and the resin loading was 0.98 mmol/g.

1.2 preparation of Fmoc-ILys (Boc) -2-chloro-trityl resin: 2-chloro-trityl chloride resin (10g, substitution 1.03mmol/g resin, leq) was added to the polypeptide synthesizer and the resin was washed with 100mL DCM. The solvent was drained and a solution of Fmoc-ILys (Boc) -OH (1.1eq) and DIEA (2.5eq) in 50mL DCM was added. The mixture was mechanically stirred for 1 hour under argon. The active fraction on the resin was blocked for 30 minutes by adding 20mL of chromatographic methanol (2mL/g resin). The solvent was drained, washed with 3X 80mL of DMF, 3X 80mL of DCM, 3X 80mL of MeOH, and dried to constant weight in vacuo to afford 14.71g of Fmoc-ILys (Boc) -2-chloro-trityl resin. And measuring the Fmoc amount in the piperidine deprotection solution by using an ultraviolet spectrophotometry, wherein the loading amount of the resin is 0.99 mmol/g.

2. Fragment preparation

2.1 first peptide fragment sequence Ac-D-2Nal-D-Phe (4-Cl) -D-3Pal-Ser (psi)^Me，Me) Preparation of Pro-OH (i.e., Ac-AA (1-4) -OH):

14.7g Fmoc-D-3-Pal-Ser (psi) was added to the peptide reaction chamber^Me，Me) Pro-2-chloro-trityl resin. The resin was swollen with 150mL of DCM and drained. The Fmoc was removed by treating the resin with 2X 150mL of 20% piperidine/DMF solution for 5, 15 minutes, respectively. The resin was washed 4 times with 100mL of DMF and the Fmoc by-product (dibenzofulvene and its piperidine adduct) and residual piperidine were removed as determined by the ninhydrin test.

Simultaneously activating the subsequent amino acid Fmoc-D-Phe (4-Cl) -OH in the sequence to react at its carboxy terminus. The Fmoc-protected amino acids (2eq), HOBt (2eq) and DIEA (4eq) were dissolved in 50mL DMF at room temperature. The solution was cooled to 0 ℃ under argon, then HBTU (2eq) was added and dissolved by stirring for 5 minutes. The activated amino acid solution was added to the drained resin and washed with 10mL DCM. The reaction was mechanically stirred for 1 hour. The completion of the condensation was monitored by a qualitative ninhydrin test. After the condensation reaction was judged complete, the resin was drained and washed with 3X 100mL of DMF.

The procedure was repeated to remove Fmoc, Ac-D-2Nal-OH 2eq was added, after condensation was complete, washing with 3X 100mL DCM, 3X 100mL MeOH, and drying in vacuo to constant weight to give 16.75g of peptide resin.

The peptide was cleaved from the resin by treatment with 400mL of 1% TFA/DCM for about 1 hour, followed by washing with 2X 50mL of 0.5% TFA/DCM for 5 minutes each. The cleaved fractions were collected on pyridine, the cleavage washes combined, concentrated under vacuum to a volume of about 30mL, then reconstituted with 20mL DMF while continuing to concentrate to remove residual DCM to a final volume of about 20mL, and the product precipitated by addition of 500mL water. The solid was collected by vacuum filtration and washed with about 500mL of water. The product was dried in vacuo to obtain 6.86g of a peptide fragment with a purity of 99%.

2.2 preparation of the second peptide fragment sequence Fmoc-4Aph (hor) -D-4Aph (Cbm-tBu) -Leu-ILys (Boc) -OH (i.e., Fmoc-AA (5-8) -OH):

to the peptide reaction chamber was added 14.7g of Fmoc-ILys (Boc) -2-chloro-trityl resin. The resin was swollen with 150mL of DCM and drained. The Fmoc was removed by treating the resin with 2X 150mL of 20% piperidine/DMF solution for 5, 15 minutes, respectively. The resin was washed 4 times with 100mL of DMF and the Fmoc by-product (dibenzofulvene and its piperidine adduct) and residual piperidine were removed as determined by the ninhydrin test.

Simultaneously activating the subsequent amino acid Fmoc-Leu-OH in the sequence to react at its carboxy terminus. The Fmoc-protected amino acids (2eq), HOBt (2eq) and DIEA (4eq) were dissolved in 50mL DMF at room temperature. The solution was cooled to 0 ℃ under argon, then HBTU (2eq) was added and dissolved by stirring for 5 minutes. The activated amino acid solution was added to the drained resin and washed with 10mL DCM. The reaction was mechanically stirred for 1 hour. The completion of the condensation was monitored by a qualitative ninhydrin test. After the condensation reaction was judged complete, the resin was drained and washed with 3X 100mL of DMF.

Repeating the procedure to remove Fmoc and activate the subsequent amino acid Fmoc-D-Phe (4-NO) in the sequence₂) -OH to react at its carboxy terminus. The Fmoc-protected amino acids (2eq), HOBt (2eq) and DIEA (4eq) were dissolved in 50mL DMF at room temperature. The solution was cooled to 0 ℃ under argon, then HBTU (2eq) was added and dissolved by stirring for 5 minutes. The activated amino acid solution was added to the drained resin and washed with 10mL DCM. The reaction was mechanically stirred for 1 hour. The completion of the condensation was monitored by a qualitative ninhydrin test. After the condensation reaction was judged complete, the resin was drained and washed with 3X 100mL of DMF. The resin was then transferred to a 250ml round bottom flask and fully activated Zn powder (15eq), CaCl added sequentially₂(0.8eq), 80% ethanol solution, refluxing, after completion of the reaction, concentrating, adding DCM solution, collecting the upper resin suspension, transferring to a polypeptide reactor, washing the resin with 3 × 100mL DMF, adding tert-butyl isocyanate (6eq) and DIEA (6eq), washing the resin with 3 × 100mL DMF after completion of the reaction.

Repeating the procedure to remove Fmoc and activate the sequenceThe subsequent amino acid Fmoc-Phe (4-NO) of (1)₂) -OH to react at its carboxy terminus. The Fmoc-protected amino acids (2eq), HOBt (2eq) and DIEA (4eq) were dissolved in 50mL DMF at room temperature. The solution was cooled to 0 ℃ under argon, then HBTU (2eq) was added and dissolved by stirring for 5 minutes. The activated amino acid solution was added to the drained resin and washed with 10mL DCM. The reaction was mechanically stirred for 1 hour. The completion of the condensation was monitored by a qualitative ninhydrin test. After the condensation reaction was judged complete, the resin was drained and washed with 3X 100mL of DMF. The resin was then transferred to a 250ml round bottom flask and fully activated Zn powder (15eq), CaCl added sequentially₂(0.8eq), 80% ethanol solution, reflux, after reaction is complete, concentrate, add DCM solution, collect the upper resin suspension and transfer to the polypeptide reactor, washing the resin with 3X 100mL of DMF. Orotic dihydrogencate (3eq), HOBt (3eq) and DIC (3eq) were added, and after completion of the reaction, the mixture was washed with 3X 100mL of DMF, 3X 100mL of DCM, 3X 100mL of MeOH, and dried under vacuum to constant weight to obtain 21.49g of peptide resin.

The peptide was cleaved from the resin by treatment with 500mL of 1% TFA/DCM for about 1 hour, followed by washing with 2X 50mL of 0.5% TFA/DCM for 5 minutes each. The lysate fractions were collected onto pyridine, pooled, and concentrated under vacuum to a volume of about 30mL, then reconstituted with 20mL DMSO while continuing to concentrate to remove residual DCM to a final volume of about 20 mL. The product was precipitated by adding 500mL of water. The solid was collected by vacuum filtration and washed with about 500mL of water. The product was dried in vacuo to obtain 11.28g of a 98% pure peptide fragment.

3. Liquid phase fragment condensation process

3.1 the third peptide fragment sequence H-Pro-D-Ala-NH₂(i.e., H-AA (9-10) -NH)₂) The preparation of (1):

weighing Fmoc-Pro-OH 10mmol and HoBt (2eq), placing in a round-bottom flask, dissolving with DMF, adding DIEA (4eq), activating, adding HBTU (2eq), H-D-Ala-NH₂HCl 10.5mmol, TLC monitor to completion of the reaction. The peptide was precipitated by adding 500mL of water. The solid was collected by vacuum filtration, washed with 2X 500mL of water, 2X 500mL of MTBE, and dried to yield Fmoc-Pro-D-Ala-NH₂. Then adding DMF to dissolve, dripping piperidine to the final concentration of 16%, and reacting for 2 hoursIn this case, ice water was added to precipitate the product, which was washed with ice water 2 times, 500mL of cold MTBE was added and stirred for 2 hours to remove the Fmoc-depleted fulvene product, and the precipitate was filtered and dried to obtain 1.8g H-Pro-D-Ala-NH₂。

3.2 fourth peptide fragment sequence H-4Aph (hor) -D-4Aph (Cbm-tBu) -Leu-ILys (Boc) -Pro-D-Ala-NH₂(i.e., H-AA (5-10) -NH)₂) Preparation of

Adding H-Pro-D-Ala-NH into a round-bottom flask₂(5.25mmol) and 6.3mmol of sodium carbonate in water, a solution of Fmoc-AA (5-8) -OSu (5mmol) in acetone was slowly added at low temperature, the reaction mixture was stirred at 0 ℃ for 30 minutes, then warmed to room temperature and stirred for an additional 4 hours. After the reaction is completed, removing acetone by rotary evaporation, adding 10% citric acid to adjust the pH value, then extracting with ethyl acetate, combining organic phases, washing with saturated NaCl, drying with anhydrous sodium sulfate, concentrating and recrystallizing to obtain Fmoc-AA (5-10) -NH₂. Adding DMF to dissolve, dropwise adding piperidine to the final concentration of 16%, reacting for 2 hours, adding ice water to precipitate the product, washing for 2 times by using ice water, adding 500mL of cold MTBE, stirring for 2 hours to remove the Fmoc-free fulvene product, filtering, precipitating and drying to obtain 5.6g H-AA (5-10) -NH₂。

3.3 Total protected Garlic Ac-D-Nal-D-Phe (4-Cl) -D-3Pal-Ser (psi)^Me，Me)Pro-4Aph(Hor)-D-4Aph(Cbm-tBu)-Leu-ILys(Boc)-Pro-D-Ala-NH₂Preparation of

Adding Ac-D-Nal-D-Phe (4-Cl) -D-3Pal-Ser (psi)^Me，Me)Pro-OH(5mmol)、H-AA(5-10)-NH₂(4.8mmol) and HOBt (5mmol) in DMF, DIEA (10mmol) was added and then cooled to 0 ℃ under argon. To the cooled solution was added HBTU (5 mmol). The reaction mixture was stirred at 0 ℃ for 30 minutes, then warmed to room temperature and stirred for a further 8 hours. The peptide was precipitated by adding 500mL of water. The solid was collected by vacuum filtration, washed with 2X 500mL water, 2X 500mL MTBE, triturated with 500mL acetonitrile at room temperature for 3 hours, collected by vacuum filtration, and dried to yield 8.63g of fully protected degarelix.

4. Degarelix cleavage and purification

4.1 preparation of crude Degarelix peptide by removal of side chain protection

150mL of a trifluoroacetic acid/water/triisopropylsilane/1, 2-ethanedithiol (92.5: 2.5) solution was added to the round-bottom flask and cooled to 0 ℃. To the cooled solution was added 8.6g of fully protected degarelix. Dissolve with stirring at 0 deg.C, then warm to room temperature and stir for 3 hours. The mixture was concentrated by rotation, and the peptide was precipitated by adding 500mL of ether at 0 ℃. Centrifugation, washing of the precipitate with 2X 500mL of ether, then dissolution of the solid in 1: 1 water/acetonitrile containing 1% acetic acid, and lyophilization afforded 7.58g of crude degarelix peptide.

4.2 HPLC purification of crude degarelix peptide

The crude degarelix peptide was purified by preparative HPLC to yield pure degarelix with a purity of 99.896% and an overall yield of 70.3%.

HPLC purification conditions: a chromatographic column: c18250 × 19, 10u, 130A; flow rate: 8 mL/min; and (3) detection: UV, 220 nm; mobile phase: A. acetonitrile; b.0.25% acetic acid/water; the method comprises the following steps: 5-25% of A for 10 min; 25-50% of A, 50 min.

Claims

1. The method for preparing degarelix by fragment condensation is characterized in that a first peptide fragment sequence protected by a side chain and a second peptide fragment sequence protected by the side chain are synthesized in a solid phase, a third peptide fragment sequence protected by the side chain is synthesized in a liquid phase, all peptide fragments are gradually coupled to obtain fully protected degarelix, then a protecting group is cracked and removed to obtain crude degarelix, and the crude degarelix is obtained by purifying and changing salt;

wherein the content of the first and second substances,

the third peptide fragment sequence is the 9 th-10 th amino acid in the degarelix sequence;

the method for preparing degarelix by fragment condensation comprises the following steps:

(6) purifying and desalting the crude degarelix peptide to obtain degarelix;

in step (1), the sequence of the first peptide fragment having side chain protection is Fmoc-D-3Pal-Ser (. psi.) (Fmoc-D-3 Pal-Ser)^Me,Me) Pro-OH, Fmoc-D-Phe (4-Cl) -OH and Ac-D-Nal-OH are coupled on a solid phase carrier in sequence to obtain; wherein, the solid phase carrier is acid-sensitive resin;

in the step (1), the second peptide fragment sequence with side chain protection is composed of amino acids Fmoc-ILys (Boc) -OH, Fmoc-Leu-OH and Fmoc-D-Phe (4-NO)₂) Coupling OH on a solid phase carrier in sequence, then reducing peptide Resin, and connecting side chain for protection to obtain peptide Resin Fmoc-D-4Aph (Cbm-tBu) -Leu-ILys (Boc) -Resin; then the peptide resin removes Fmoc protection and amino-terminal coupling Fmoc-Phe (4-NO)₂) OH, then reducing the peptide Resin, and carrying out side chain protection to obtain Fmoc-4Aph (hor) -D-4Aph (Cbm-tBu) -Leu-ILys (Boc) -Resin; wherein, the solid phase carrier is acid-sensitive resin;

in the step (2), the sequence of the side chain-protected third peptide fragment Fmoc-Pro-D-AIa-NH₂From Fmoc-Pro-OH and D-Ala-NH₂Coupling in liquid phase.

2. The method for preparing degarelix by fragment condensation according to claim 1, wherein in the step (1), in the solid phase synthesis of the sequence of the first peptide fragment protected in the side chain, the amino group deprotecting reagent used is a DMF solution of piperidine with 20% by volume or a DMF solution of DBU with 1% by volume; the coupling agent is the combination of DIC and HOBt, or the combination of HBTU, HOBt and DIEA, or the combination of PyBOP, HOBt and DIEA; the cracking agent is a DCM solution of TFA with the volume percentage of 0.5-1%, a DCM solution of TFE with the volume percentage of 20%, or a mixture of TFE, AcOH and DCM according to the volume ratio of 1:2: 7.

3. The method for preparing degarelix by fragment condensation according to claim 1, wherein in the step (1), in the solid phase synthesis of the sequence of the second peptide fragment with side chain protection, the amino deprotection reagent is a DMF solution of piperidine with a volume percentage of 20% or a DMF solution of DBU with a volume percentage of 1%; the coupling agent is the combination of DIC and HOBt, or the combination of HBTU, HOBt and DIEA, or the combination of PyBOP, HOBt and DIEA; the cracking agent is a DCM solution of TFA with the volume percentage of 0.5-1%, a DCM solution of TFE with the volume percentage of 20%, or a mixture of TFE, AcOH and DCM according to the volume ratio of 1:2: 7.

4. The process for preparing degarelix by fragment condensation according to claim 1, wherein in step (2), the coupling agent used is a combination of HBTU and HOBt and DIEA, or HBTU and hoaat and DIEA, or DIC and HOBt, or EDC and HOBt, or PyBOP and HOBt and DIEA; the solvent for the coupling reaction is any one or a combination of several of DMF, DCM, NMP, THF, TFE and DMSO.

5. The method for preparing degarelix by fragment condensation according to claim 1, wherein in step (3), the amino deprotection reagent is used as a DMF solution containing 16% by volume of piperidine or a DMF solution containing 1% by volume of DBU.

6. The process for preparing degarelix by fragment condensation according to claim 1, wherein in steps (3) and (4), the coupling agent used is a combination of HBTU and HOBt and DIEA, or a combination of HBTU and HOAt and DIEA, or a combination of DIC and HOBt, or a combination of EDC and HOBt, or a combination of PyBOP and HOBt and DIEA; the solvent for the coupling reaction is any one or a combination of several of DMF, DCM, NMP, THF, TFE and DMSO.

7. The method for preparing degarelix by fragment condensation according to claim 1, wherein in step (5), the cleavage solution for cleaving the fully protected degarelix is TFA and H₂Mixed solution of O in a volume ratio of 95:5, or TFA and EDT and TIS and PhOH and H₂Mixed solution of O in a volume ratio of 80:5:5:5:5, or TFA and EDT and TIS and H₂And O is mixed solution according to the volume ratio of 92.5:2.5:2.5: 2.5.

8. The method for preparing degarelix by fragment condensation according to claim 1, wherein in the step (6), the purification is reversed-phase high performance liquid chromatography for purifying salt exchange; the mobile phase is acetic acid water solution and acetonitrile solution.